This invention relates to a pump which can repeatedly discharge a precise amount of fluid. More particularly, this invention relates to such a pump with improved, repeated accuracy in that deleterious water hammer is eliminated and internal dead air space is minimized.
Fluid metering pumps are well known in the art. In these types of pumps, it is desirable that a precise amount of fluid be repeatedly discharged from the pump. Repeated, accurate operation of the pump can be critical in many applications, such as operation in the medical field.
A typical prior-art metering pump is piston diaphragm operated and includes vertically-spaced inlet and outlet valve assemblies with a pump chamber therebetween. An actuating assembly is normally positioned laterally of the pump body and communicates with the pump chamber through a diagonally oriented passageway. The actuating assembly includes a solenoid-actuated piston or plunger which carries a diaphragm. When the solenoid is actuated, the piston moves the diaphragm to draw fluid in through the lower inlet valve and into the pump chamber and the diagonal passageway. Then, when the solenoid is disengaged, a return spring pushes the diaphragm downwardly to force fluid out of the diagonal passageway and the pump chamber, and out through the discharge valve located vertically above the inlet valve. The volume of the fluid to be pumped with each stroke of the plunger can be controlled by regulating the extent of the stroke of the plunger.
These types of pumps do not always provide repeated, accurate fluid discharge for at least two reasons. First, air pockets of an inconsistent and/or unpredictable size will tend to form around the diaphragm of these prior-art pumps. As such, due to the inconsistencies of the compressibility of the air, consistency or repeatability of the pumped fluid output is not readily obtainable.
The other major problem which results in inconsistencies of the fluid output of these prior-art pumps is the existence of the water hammer phenomena. That is, when the plunger strokes to allow the diaphragm to pull fluid in through the inlet, all of the fluid in the conduit between the inlet and the source of supply is set in motion. As a result, when the valves want to close at the end of a stroke, the momentum of the moving fluid will continue to push on the inlet valve to potentially expel an undesired and potentially unmeasurable amount of fluid through the outlet valve.
Thus, the need exists for a pump which can repeatedly meter the desired amount of fluid to be discharged therefrom.
It is thus an object of the present invention to provide a pump which delivers the same amount of fluid upon each actuation thereof.
It is another object of the present invention to provide a pump, as above, which minimizes any dead air space.
It is a further object of the present invention to provide a pump, as above, which significantly reduces the potential for a water hammer effect on the quantity of the pumped fluid.
These and other objects of the present invention, as well as the advantages thereof over existing prior-art pumps, which will become apparent from the description to follow, are accomplished by the improvements hereinafter described and claimed.
In general, a pump made in accordance with one aspect of the present invention includes a pump body having a fluid inlet and a fluid outlet. A first valve is positioned in the fluid inlet, and a second valve is positioned in the fluid outlet. A connector having a bend is formed at the fluid inlet. When the pump is activated, fluid is drawn in around the bend, through the inlet and first valve, into the pump body, and fluid passes out through the second valve and the fluid outlet.
In accordance with another aspect of the present invention, the pump includes a chamber. A fluid inlet is positioned laterally to one side of the chamber, and a fluid outlet is positioned laterally to the other side of the chamber. The fluid inlet and outlet communicate with the chamber above the centerline of the fluid inlet and fluid outlet. When the pump is activated, fluid is received through the inlet, into the chamber, and fluid passes out through the outlet.